MSD Manual

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Anthelmintic compounds for helminthiasis approved in the USA

Anthelmintic compounds for helminthiasis approved in the USA


Spectrum of activity


Withdrawal time

Further considerations

Piperazine compounds

Ascaridia spp.

Chickens: Single dose, 50 mg/bird (< 6 weeks old), 100 mg/bird (≥6 weeks old), in the feed at 0.2%–0.4% or in the drinking water at 0.1%–0.2%

Turkeys: Single dose 100 mg/bird (< 12 weeks old) or 200 mg/bird (≥12 weeks old)

Because only the piperazine moiety is efficacious, doses should be calculated based on mg of active piperazine/bird. Treatment can be repeated after 14 days.

14 days (meat); not approved in the USA for birds producing eggs for human consumption.

Relatively nontoxic. Resistance is widespread. Piperazine should be completely consumed by birds within a few hours, because only relatively high concentrations of the drug eliminate worms. Some practitioners recommend the addition of molasses to unmedicated water after piperazine administration to induce an osmotic flushing, theoretically removing any of the remaining worms from the intestinal tract.


Ascaridia spp, Heterakis gallinarum

Growing turkeys: 14.5 g/ton of feed (16 ppm), fed continually as the sole ration for 6 days.

None for turkeys

Not approved for other poultry.

It has been suggested that an alternative drug be used for treatment of breeding toms or that the sperm number and frequency of artificial inseminations be increased.

Fenbendazole should not be administered during molt, because it may interfere with feather regrowth.

Hygromycin B

Ascaridia spp, Heterakis gallinarum, Capillaria spp.

8–12 g/ton in feed

3 days for meat


Capillaria spp.

Replacement pullets: 0.004% in feed for 10–14 days

Layers: 0.003% in feed for 14.

Chickens < 8 weeks old should not be given this medication.

In birds maintained on contaminated litter or exposed to infected birds, the medication regimen should be repeated using the same dosages as the first. There should be at least 3 weeks between the first and second course of treatment.


Coumaphos is a cholinesterase inhibitor with a low therapeutic index. Treated birds should not be exposed to other cholinesterase inhibitors (drugs, insecticides, pesticides, or chemicals) within 3 days before or after treatment. It should not be used within 10 days of vaccination or other stress.


Syngamus trachea

Pheasants: 0.05% in feed for 14 days

21 days for meat

Specific precautions should be observed in feeds containing bentonite